Blast furnace taphole plugs

ABSTRACT

This invention relates to anhydrous plugs for stopping the tapholes of blast furnaces. This plug comprises, as a basic refractory material, a mixture consisting of low alumina pure silica and one or more refractory or gritty clays, and, as a binder, a resin or a plastic material containing a setting retarder such that the plug be heat stable at about 200* C.

United States Patent Inventor Pierre Elby 76 Rue du Chlvaire, Berck, Sur-mer 62, France Appl. No. 657,499 Filed Aug. 1, 1967 Patented Sept. 21, 1971 Priority June 28, 1967 France 1 12,264

BLAST FURNACE TAPHOLE PLUGS 4 Claims, No Drawings U.S. Cl 260/28, 260/28.5, 164/43, 260/30.6, 260/57, 260/72, 260/847, 260/853, 266/42, 266/43 Primary Examiner-Morris Liebman Assistant Examiner-H. H. Fletcher Attorneys-Robert E. Burns and Emmanuel J. Lobato ABSTRACT: This invention relates to anhydrous plugs for stopping the tapholes of blast furnaces. This plug comprises, as a basic refractory material, a mixture consisting of low alumina pure silica and one or more refractory or gritty clays,

and, as a binder, a resin or a plastic material containing a setting retarder such that the plug be heat stable at about 200 C.

FIELD OF THE INVENTION This invention relates to the manufacture of anhydrous masses or plugs for stopping the tapholes of blast furnaces.

DESCRIPTION OF THE PRIOR ART Since the existence of the earliest blast furnace, it has always been necessary to temporarily plug the taphole during the pig-iron-refining process.

For many years blast furnace tapholes have been stopped by using water-containing plugs or masses. As production increased, together with the size and power rating of the blast furnaces themselves, these masses did not provide the safety consistent with a satisfactory plugging. The taphole wall was easily worn away by the flow of molten pig iron, castings became irregular and some means had to be used for retarding the flow or reducing the pressure at each casting. Moreover, the introduction of water into the blast furnace was attended by a rapid disintegration of the inner lining of the crucible; thus, the dislodgment of the clay lining as a consequence of a mechanical destruction process, or the disintegration of the carbon lining as a consequence of a high-temperature chemical reaction, were currently observed. This resulted in very serious break holes causing a complete holdup of the blast furnace. The development of anhydrous stopping plugs was considered as a substantial improvement. They consist as a rule of a mass or paste made of 20 percent of coking plant tar, percent of powdered coke or coal and 70 percent of an aggregate of refractory materials, these powders being ground to a suitable mesh size, well known to manufacturers; the resulting masses became extremely hard after firing so that the tapholes were no more worn away by the outflowing cast iron. Thus, it was no longer necessary to slow down the blast furnace operation at each casting, whereby a substantial gain was achieved in the daily production.

As these plugs or masses are anhydrous, the inner lining of the crucible was no longer attacked by the water content of previously used water masses, and the taphole troubles disappeared. Besides, the quantity of mass required for stopping a taphole was reduced by one-half. However, anhydrous masses are not perfect and various in conveniences are ascribable thereto.

The coking operation necessary for hardening the plug material makes it necessary to insert a stopper gun for a period of about 1 hour into the taphole; the space thus occupied in front of the blast furnace and in the main clay-lined trough or runner is particularly detrimental to the blast furnace operators or casters who are confronted with the difficult task of cleaning and repairing this trough or runner between successive castings.

If the castings take place at relatively short intervals, the time available for allowing the paste located inside the blast furnace to be fired completely is too short and when the plug is removed clots of unfired tar appear which produce flames thrown at relatively great distances, and likely to injure the men working on the front area of the blast furnace.

Besides, the tar smell released by the anhydrous masses are extremely unpleasant and, sometimes, according to the nature of the tar contained in the paste, this smell is hardly bearable by the operators and causes discomfort and vomiting among the casting crew.

According to the quality of the anhydrous masses used for stopping the tapholes, cleaning the taphole plugger is sometimes difficult for it happens that the mass hardens therein; this is attended not only by a loss of material but also by a considerable loss of time for the operators who must clear and prepare the taphole plugger for the next casting. The consistency of this paste is relatively hard and particularly powerful plugging units are necessary for introducing it into the taphole of blast furnaces.

SUMMARY OF THE INVENTION With the new technique using special quick-hardening masses according to this invention all these serious inconveniences are definitely eliminated.

The plug mass hardens at a very fast rate in the taphole and therefore the plugger can be withdrawn from the taphole 10 to 15 minutes after the plugging. Under these conditions, the works for reconditioning the casting trough or channel can be carried out more easily. In certain cases the gain of time permits a reduction of the number of men comprising the casting crew.

As the plug mass does not harden within the plugging gun, the cleaning of this gun is much easier for the men entrusted with this task.

Several castings at relatively short time intervals can be performed without the inconvenience of finding unfired tar inclusions; thus, any danger is removed and the operators safety is complete. The taphole is not worn away and the castings take place smoothly and regularly, thus avoiding any casting channel erosion and increasing the useful life of the elements involved.

The smell released from this paste is particularly light and cannot cause discomfort to the crew.

The use of a binder in the plug mass, according to a specific feature of the present invention, improves the plasticity of the mass mixed with tars. Therefore, the improved mass according to this invention can be thrusted into the taphole by using taphole-plugging units of lower power rating, thereby enabling smaller concerns or plants to avoid the cost of powerful and therefore very costly plugging machines.

The improved quick-hardening mass according to this invention is adaptable to the crucible of the blast furnace and constitutes a perfect lining for the internal wall of the crucible. Due to its quick-setting and high-hardness properties, it eliminates cast-iron infiltrations sometimes found after 40- inch to 45-inch drilling, which make drilling operations particularly difficult and costly due to the frequent breakage of drills.

With the plug mass composition according to this invention all the major difficulties experienced by blast furnace operators in connection with the vital point constituted by the taphole are now removed. This improved composition can be used irrespective of the type of inner lining of the blast furnace and whatever the kind of pig iron produced therein (Hematite Fe Q- L. D., Thomas, Martin, etc.)

DESCRIPTION OF THE PREFERRED EMBODIMENTS Two essential features characterize the present invention: On the one hand, the composition of the refractory charge and on the other hand the heat-stable binder acting as a quickhardener therein.

IREFRACTORY CHARGE The basic refractory materials commonly used in the manufacture of anhydrous masses consist as a rule either of natural sands or of natural clays. Experience teaches that the use of these materials is attended by the following inconveniences:

a. If natural raw sands as obtained from sand pits are used, it

is a frequent occurrence that their alumina contents approaches the eutectic value. Under these conditions the melting point drops considerably and the plug strength becomes substantially zero.

b. If the sand is abnonnally lean, the mass has no cohesion, a poor plasticity and the piston of the plugging machine becomes jammed and cannot thrust the paste into the taphole.

. If clays are used the absorption power thereof is such that a few hours after its manufacture the mass hardens too much and abnormally high binder contents must be used to obtain a satisfactory plasticity. THis leads to a poor coking process and a reduction in the mass hardening time. Moreover, considerable smells and smokes are released during the plugging operation.

d. After firing and coking the clays shrink considerably so that the mass introduced into the taphole does not adhere adequately to the walls, thus developing cracks into which the liquid pig iron can seep.

In view of these negative reasons, the first feature characterizing this invention consists in using, as a basic refractory material, a mixture consisting of pure silica (quartz sand) having a very low alumina content (not in excess of 3 to 4 percent) and of one or a plurality of refractory or gritty clays.

The alumina content of the mixture is selected to keep the silica/alumina ratio as remote as possible from values likely to promote the development of an eutectic structure. Silica was the preferential choice because this material expands and tends to offset the shrinking of clay. As the mass hardens it adheres strongly to the walls of the taphole without producing cracks therein. On the other hand, as the absorption power of silica is very low, a lower amount of binder is required to produce a quick-setting plastic paste.

II-l-IEAT-STABLE BINDER ACTING AS A QUICK- HARDENER in most instances this material is commonly referred to as a natural or synthetic resin (or) plastic material, and is thermosetting This organic material, owing to its wetting properties, acts as a fluidizer and homogenizer during the manufacture of the plug mass. It also acts subsidiarily as a quickhardener during the plugging operation proper when, by heat conductibility, the heat gradually spreads through the plug mass, and furthermore this organic material promotes the setting of the plug mass within about to minutes.

However, once again experience teaches that adding a resin or any aldehyde phenol or aldehyde amine to the basic binder (usually tar) led to the following drawbacks:

To obtain the quick-setting feature it is obviously necessary to add an amount sufficient and necessary to reduce the polymerization and coking time to 10 to 15 minutes, considering 10 minutes as a minimum since the withdrawal of the plugging machine is unnecessary before the end of this time period, as the pig iron is still liquid in the casting channel and prevents the operators from going down into it to recondition the channel walls. Now in practice the addition of a resin, even in small amounts (of the order of 2 to 5 percent) makes the mass extremely difficult and sometimes impossible to use.

In fact, it was proved by actual industrial practice that plug masses thus prepared had all the requisite properties of first quality taphole plugs at the first application, but as these masses are reconditioned the tapholes lost more and more their original tightness and eventually the plugs became unsuitable for properly sealing the taphole.

In fact, after each plugging operation the last furnace operators feed fresh paste into the plugging machine as a substitute for the paste previously discharged during the preceding plugging operation. Now plugging machines are compulsorily exposed to extremely high temperatures either during the plugging operation proper or subsequently, due to the heat radiation resulting from their position very close to the casting channels, and under these conditions the paste kept inside the machine is gradually converted and an undesirable slow coking process takes place. The plasticity of the mass decreases and a porous condition develops, whereby the subsequent coking process is compromised' Thus, it is customary to introduce into the taphole a product of reduced strength and quality, which will very soon become unusable as a plugging mass.

The conditions of operation of all blast furnaces are such that this mass cannot be properly used unless the plugging machine is carefully cleaned after each taphole plugging and fresh paste, which has not been exposed beforehand to the normal operating temperature of this machine, is introduced into it.

The other feature characterizing this invention consists in utilizing as a binder-hardening substance a resin and a settingretarding agent such that the product be heat stable at about 200 C.

The resin may be selected from the group comprising phenoplasts and aminoplasts. The anhydrous mass may further include materials selected from the group consisting of polyvinyl chloride, benzyl alcohol, and tricresyl phosphate.

The binder pH value should range from 6 to 7.4.

With the present invention the paste can be used with the maximum safety and under practical operating conditions, thus affording considerable savings of material, labor and time.

The basic materials such as the quartz sand and the heat stable adjuvant afford a competitive cost, and furthermore the amount of mass to be introduced into the taphole is reduced by one-half in relation to conventional masses.

The following examples illustrate a few formulations of blast furnace plugging masses according to this invention.

EXAMPLE I.

Refractory material 68% (34% sand, 18% clay) Coke over tar l 1% Liquid tar l7% Resol-type phenol resin 3.5%

Setting retarder (polyvinyl chloride) 0.5%

EXAMPLE 2.

Sand and clay 69% (35% sand+34% clay) What I claim is:

1. In an anhydrous mass for plugging blast-furnace tapholes comprising refractory clay and silica sand with tar as a hinder, the improvement which comprises including in said mass approximately 2 percent to 5 percent of a thermosetting resin selected from the group consisting of phenoplasts and aminoplasts and heat stable at 200 C. and a material selected from the group consisting of polyvinyl chloride, benzyl al cohol, and tricresyl phosphate, said sand containing not more than 4 percent of alumina.

2. An anhydrous mass according to claim I, in which the resin comprises a phenoplast.

3. An anhydrous mass according to claim I, in which the resin comprises an aminoplast.

4. An anhydrous mass according to claim I, in which the pH of said resin is between 6 and 7.4. 

2. An anhydrous mass according to claim 1, in which the resin comprises a phenoplast.
 3. An anhydrous mass according to claim 1, in which the resin comprises an aminoplast.
 4. An anhydrous mass according to claim 1, in which the pH of said resin is between 6 and 7.4. 